Electric vehicles in which left and right transporting parts are driven by left and right electric motors are known from for example JP-A-57-78855, JP-A-57-85505 and JP-A-2001-271317. When transporting parts are driven by electric motors like this, there is the advantage that the electric vehicle can be made relatively maneuverable.
A snow-clearing machine disclosed in JP-A-2001-271317 will now be described briefly on the basis of FIG. 19 hereof.
In FIG. 19, a snow-remover 200 has on a machine body 201 a working part 204 made up of an auger 202 and a blower 203; an engine 205 for driving the working part 204; left and right transporting parts 206, 206 consisting of crawlers; left and right electric motors 207, 207 for driving these transporting parts 206, 206; a generator 209, driven by the engine 205, for supplying electrical power to a battery 208 and the electric motors 207, 207; and a control part 211 for controlling the electric motors 207, 207.
Some of the output of the engine 205 is used to drive the generator 209, and the electrical power obtained is supplied to the battery 208 and the left and right electric motors 207, 207. The remainder of the output of the engine 205 is allocated to rotating the working part 204 via an electromagnetic clutch 212. Thus, in this snow-remover 200, the working part 204 is driven by the engine 205 and the transporting parts 206, 206 are driven by the electric motors 207, 207.
Now, an ordinary snow-remover 200 has left and right operating handles extending rearward from the rear part of the machine body 201 and has grips on the ends of these left and right operating handles. Brake levers (turning levers) are provided beneath these grips, and by gripping one of these brake levers it is possible to make the electric vehicle 200 turn by decelerating the electric motor 207 corresponding to the gripped lever, that is, the electric motor driving the transporting part constituting the turning center (hereinafter, ‘the motor on the inside of the turn’).
However, because the turning described above is lever-controlled, the degree of deceleration of the motor 207 on the inside of the turn varies with the degree of gripping of the lever. And because it requires a certain amount of skill in turning control to make the snow-remover 200 turn in accordance with the turning operation feel of the operator while keeping the snow-remover 200 traveling through the turn, there has been room for improvement.
Also, in the snow-remover 200 described above, because levers are used as the turning control means, in each turning control means an error arises in the relationship between the lever control level and the corresponding control signal level. The work of adjusting for this error is troublesome, and there has been a need for adjustment of the turning control means to be rendered unnecessary.